# Is is-async-function ESM-only? Can you require() it?

> is-async-function@2.1.1 is a CommonJS package. CommonJS — require() works on every Node.js version we test.

Determine if a function is a native async function.

Last verified Sep 9, 2026 against is-async-function@2.1.1.

is-async-function ships CommonJS only. require("is-async-function") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. The package declares Node.js >= 0.4. import "is-async-function" also works because Node.js and Bun can import CommonJS from ES modules, but only the default export is guaranteed; named imports depend on Node's static analysis of the module.

## What to do

1. require("is-async-function") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. The package declares Node.js >= 0.4.
2. From ES modules use the default import: import isAsyncFunction from "is-async-function"; then destructure. Named imports only work when Node.js can statically detect the exports.
3. TypeScript: types are bundled; install nothing extra.

## Facts

- Latest: 2.1.1 (Jan 23, 2025)
- Module format: CommonJS
- Last CommonJS version: 2.1.1
- TypeScript types: bundled
- Node engines: >= 0.4
- Weekly downloads: 68.5M
- License: MIT

## Runtime test results for is-async-function@2.1.1

Installed and executed on Sep 9, 2026 with require("is-async-function") from a CommonJS file and import "is-async-function" from an ES module.

| Runtime | require("is-async-function") | import "is-async-function" |
|---|---|---|
| Node.js 18 | works | works |
| Node.js 20 | works | works |
| Node.js 22 | works | works |
| Node.js 24 | works | works |
| Node.js 26 | works | works |
| Bun 1.4.0 | works | works |

## How to import is-async-function

ES modules:

```js
import isAsyncFunction from "is-async-function";
```

CommonJS:

```js
const isAsyncFunction = require("is-async-function");
```

## Module format by version

Derived from the type, main and exports fields of every stable release on npm (17 versions; the newest 17 shown).

| Versions | Format | First published |
|---|---|---|
| 0.0.0 – 2.1.1 | CommonJS | Jun 5, 2015 |

## Frequently asked

**Is is-async-function ESM-only?**

is-async-function@2.1.1 is a CommonJS package. is-async-function ships CommonJS only. require("is-async-function") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. The package declares Node.js >= 0.4. import "is-async-function" also works because Node.js and Bun can import CommonJS from ES modules, but only the default export is guaranteed; named imports depend on Node's static analysis of the module.

**Can I import is-async-function with ES module syntax?**

Yes. import isAsyncFunction from "is-async-function" works in Node.js and Bun because they support importing CommonJS modules. Named imports work only when Node.js can statically detect the exports.

**Does is-async-function work in Bun?**

Yes. import "is-async-function" loaded successfully in Bun 1.4.0 on Sep 9, 2026.

**Does is-async-function ship TypeScript types?**

Yes. is-async-function bundles its own type declarations; no @types package is needed.

## Links

- [is-async-function on npm](https://www.npmjs.com/package/is-async-function)
- [Source repository](https://github.com/inspect-js/is-async-function)
- [HTML version](https://canirequire.com/package/is-async-function/)
- [JSON version](https://canirequire.com/package/is-async-function.json)

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